Moved font height into loading function

  - Font height must be specified when loading a font face
  - Cannot be changed afterwards
Added expose event

  - Could be used to draw a window background
  - Can be used with OpenGL to use normal main loop and redraw on demand
    instad of pumping out images at maximum frame rate
Fitted event enum into coding style, seperated widget/window events

  - defines instead of enum (event and key codes)
  - seperated values of window, widget manager and widget events

  - EDIT: apparently broke either utf8 reading or rendering (test with
    edit box)
Fixed UTF8 rendering

  - Decoder got fucked up at some point in the past
    -> Unitinialised length
    -> Messed up bit fiddling
  - Fixed now with cleaner, simpler implementation that works